DESCRIPTION: Assessing exposures of workers to chemical hazards is an essential element of occupational epidemiology and industrial hygiene. However, exposure assessment is often the weakest link in research on the relationship between chemical exposure and occupational disease. Thus, development of a more reliable basis for worker exposure assessment methods is a critical need. The long-term goal of the research proposed here is develop more reliable exposure assessment methods by investigating how physical factors in a workroom govern worker exposure and its variation. These factors include work area airflow characteristics, work area physical configuration, source characteristics, and worker activities.